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IERI Procedia 5 ( 2013 ) 232 – 237

2212-6678 © 2013 The Authors. Published by Elsevier B.V.Selection and peer review under responsibility of Information Engineering Research Institutedoi: 10.1016/j.ieri.2013.11.097

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Available online at www.sciencedirect.com

© 2013 The Authors. Published by Elsevier B.V.Selection and peer review under responsibility of Information Engineering Research Institute

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233 Nahid Ghasemi et al. / IERI Procedia 5 ( 2013 ) 232 – 237

Introduction

Removal of heavy metals in treatment of wastewater has long been considered. The research of adsorption is important because it provides noteworthy viewpoint into the reaction trajectory and the mechanism of sorption reactions, also demonstrates the solute adsorbed rate[1]. According to Ho studies on sorption is provided PS-order rate expression[2]. Also, Azizian reported the analysis of a theoretical model of PS-order [3]. For low initial concentration from a solute, the Azizian’s extraction has advantage because the sorption process will follow the PS-order model. The first advantage of PS-order equation is that it doesn’t have any problem to assign a capacity of effective sorption. Also the rate of initial sorption, the capacity of sorption and the PS-order constant rate can be determined from the equation with unknown parameter. The final advantage is that by using batch reactions at various concentrations of initial sorption, different particle sizes, speeds of agitation, doses of sorbent, values of pH and different temperatures, the type of sorbent and sorbate, the kinetic studies can be carried out.

In this research, the pistacia atlantica shells was applied for the adsorption of Pb (II) ions from wastewater as adsorbent. The research focuses on adsorption kinetics studies of the prepared adsorbent and four PS-order kinetic linear equations have been applied to test.

1. Experimental

1.1. Materials and methods

The experiments were conducted using pistacia atlantica shells obtained from Eilam-Iran. At first it was washed five times with hot deionized water to take the impurities, and was then dried at 105 oC for 24 h in an oven, and was after screened with a sieve (120 mesh). The sieved pistacia atlantica shells was soaked with H2SO4 at 1:1 ratio for overnight. The acidic solution was then removed, and the pistacia atlantica shells was rinsed until the pH=7 with distilled water to remove excess H2SO4. The powder obtained from the pistacia atlantica shells become dry for 2 h at 105°C. The main solution of Lead nitrate (1000 mg L-1) was ready with purified water using Lead nitrate salt. Different concentrations of solutions of Pb (II) are ready from the main solution when necessary.

The pistacia atlantica shells (0.1 gr) was added to a 120 mL Erlenmeyer containing 70 ml of 100 mg L-1 of Pb(II) with pH =4, stirred at 150 rpm and at temperature 298 K. Samples were taken at proper time intervals (5-120 minutes) and the filtrate analysed by Atomic Absorption Spectrophotometer (AAS). By using HNO3 or NaOH (0.1N), initial pH was adjusted.

PS- order

The PS-order kinetic rate equation [4] which is generally extracted in Equation (1):

(1)

Where k(gmg-1min-1) is PS-order rate constant of adsorption, qe and qt (mgg 1) are named the adsorption capacity at time of equilibrium and t. Integrating Equation (1) with applying border conditions t=0 and t=t , qt=0and qt=qt , gives:

(2)


In general, due to its simplicity, the PS-order kinetic has been widely applied in the designing of very adsorption methods[5]. Sinc the PS-order which explained by Equation (2) is non linear, seem that appraising the value of qe and the rate constant of adsorption k needs adjusting the equation to empirically results by non linear of regression applying methods of numeric optimization. A proper choice for non-linear of regression is to apply linearized variants of the equations that the PS-order kinetic could be linearized to four versions (Table 1) for the calculation of parameters of qe and k [6].

Table 1. PS-order kinetic linearized forms [6]

(Fig. 1) and (Fig. 2), linearized versions 1 and 2 of the PS-order kinetic equations have t/q and 1/q on their

Y axis, that amounts of numeric low of Y whereas q is great. As observed in linearized versions equations 2 and 3 (Fig. 3), in t and q, the errors of the experimental distribution, if the axises be the versus 1/t or 1/q will change. There is also a difficulty in incorrect relation in linearized versions 1, 3 and 4(Fig. 4). It often takes place that the proportional relation of variables was applied to make of a variable relationship among the variables their selves [6]. An empirical error was presented in the X axis variable, as in linearized versions 3 and 4 observed, if the axis of X is (q/t or q), many experimental methods have unimportant errors in measuring t.

Fig. 1. linearized versions-1 equation of PS-order obtained during the adsorption of Pb(II) by using pistacia atlantica shells

linearized versions equation

1 =

2

3

4




All of parameters for four linearized versions of PS-order kinetic equations included qe and k and the coefficient of determination, R2 listed in Table 2. These parameters were determined from the slope time and the intercept of a straight line according to equations that given in Table 1.

y = 2.283x + 44.91R² = 0.646

0

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Conclusions

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References

[1] Ho Y S, Mckay G. Pseudo-second order model for sorption processes. Process Biochemistry 1998; 34: 451-465. [2] Ho Y S. Pseudo-Isotherms Using a Second Order Kinetic Expression Constant. Adsorption 2004; 10: 151–158. [3] Ho Y S. Second-order kinetic model for the sorption of cadmium onto tree fern: a comparison of linear and non-linear methods Water Res 2006; 40: 119–125. [4] Bhattacharyya, K.G, Sharma A. Adsorption of Pb(II) from aqueous solution by Azadirachta indica (Neem) leaf powder. J. Hazard. Mater 2004; B113: 97–109. [5] Ho Y S. Review of second-order models for adsorption systems. J. Hazard. Mater 2006;136: 681–689. [6] M.I. El.Khaiary, G.F. Malash, Y.S.Ho ,On the use of linearized pseudo-second-order kinetic equations for modeling adsorption systems. Desalination 2010; 257: 93–101.

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